With the arrival of Christianity and its literary promulgators, St. Patrick and St Columba, authentic history may be said to have begun, first in Ireland, and then in Scotland. Before the fifth century there existed a rich and abundant saga literature transmitted by oral tradition. But even the very oldest of the tales we now have, could hardly have been written down in MS. form before the seventh or eighth century. Such is the general belief of scholars who have sifted and examined the earliest records. The mass of saga carried over from pagan times, goes back over ages untold and immemorial. And yet it is found to sort out under great leading periods or cycles, three of which seem to stand out distinct and pre-eminent. These are known as the Mythological, the Heroic, and the Ossianic. Roughly speaking, the Mythological cycle, beginning away back in the vague and dim past, stretches to near the beginning of the Christian era. The other cycles follow, filling up the 400 odd years that elapse before the dawn of written history. The mythological stories are fewer than the rest, and of course more absurd and unintelligible. Most of them are found in O’Clery’s _Leabhar Gabhala, or Book of Invasions_, 1630, of which the more important MSS. are the Books of Leinster and Ballymote. Their chief interest lies in the light they throw upon the early religious ideas of the Celt. In a practical age like our own, most people are impatient of ancient myth and fairy tales. They seem so utterly unreal, absurd, and impossible, that it is hard to conceive how any sane mortal could have given them credence for one moment. And yet so universal are such stories among every race of mankind, and so credible and far-reaching in their influence in early times, that they have survived when multitudes of recorded facts have perished. They show that men, and especially primitive men, have the same kind of thoughts, desires, fancies, habits, and institutions all the world over. The myths and folk-tales have a wonderful similarity, reappearing in different guise but in substance the same, among the most varied races and peoples, so that savages to-day in different continents and islands have beliefs and customs corresponding to those which stagger us in the sagas of our own Celtic ancestors, and quite as fantastic.